1. Field of the Invention
The present invention relates to the monitoring of the orthopedic motion of a person and, more particularly, to the measuring of foot contact time, foot loft time, speed and/or pace of a person in locomotion.
2. Discussion of the Related Art
It is known that useful information may be derived from the measurement of the "foot contact time" of a person in locomotion, wherein "foot contact time" refers to the period of time that a foot of a person is in contact with the ground during a stride taken by the person. Once the foot contact time of a person is known, other information, such as rate of travel, distance traveled and ambulatory expended energy may be calculated based upon this measured foot contact time.
In the past, foot contact time has been measured by placing pressure-sensitive sensors or switches, such as resistive sensors, in both the heel and toe portions of the sole of a shoe, and measuring a time difference between a first signal output by the heel sensor (which indicates that the foot has made physical contact with the ground) and a second signal output by the toe sensor (which indicates that the foot has left the ground). These sensors, however, are subjected to a high-impact environment inside of the shoe, and therefore fail frequently. In addition, inaccurate foot contact time measurements may result when a user is taking strides during which either the heel sensor or the toe sensor is not activated, for example, when a user is running on his or her toes.
Another device well-known in the art is a pedometer. A pedometer typically is mounted on the waist of a user and is configured to count the footsteps of the user by measuring the number of times the user's body moves up an down during footsteps taken by the user. A well-known prior art pedometer design uses a weight mounted on a spring to count the number of times that the user's body moves up and down as the user is walking. By properly calibrating the pedometer according to a previously measured stride length of the user, the distance traveled by the user may be measured by this device. These "weight-on-a-spring" pedometers, however, generally cannot measure the distance traveled by a runner because the weight experiences excessive bouncing during running and footsteps are often "double-counted" because of this bouncing, causing the pedometer to produce inaccurate results. These devices, therefore, may not be used across different training regimes (e.g., walking, jogging, and running).
Another prior art pedometer device uses an accelerometer to measure the number of times that a foot impacts the ground when a user is in locomotion. That is, an accelerometer is mounted on a shoe so as to produce a signal having pronounced downward going peaks that are indicative of moments that the foot impacts the ground. These devices therefore produce results similar to the prior art weight-on-a-spring pedometer devices in that they merely count the number of footsteps of a user, and must be calibrated according to the stride length of the user in order to calculate the distance traveled by the user. Thus, these accelerometer-based devices are subject to similar limitations as are the weight-on-a-spring devices, and are not able to measure the foot contact time of a user in locomotion.
It is therefore a general object of the present invention to provide a new approach to pedometry that is affordable, reliable, easy to use and accurate.